Ah, poor baby! We went through the same thing with our dog a few months ago. One thing I can assure you though is that dogs rarely have a reaction that limits their breathing. I got this from the vet at the Humane society that I volunteer at. Dogs are not built that way so hopefully that relieves some of the stress of worrying. I know I had the same fear when Mollie was all swollen up.

Here's hoping the benadryl works quickly!